ESC Fried, need help from a electical expert

[Sympster]

I was planning to use a Hobbico Red Hawk 3 channel radio on a 2 channel vectored trust plane to 3 channel A/E/T conversion. I decided to test the amount of amps the Red Hawk motor was pulling, so using a DVM I cut one of the leads going from the esc to the motor and clipped the DVM inline (I know this was my mistake now, I should have done it at the battery). Anyway, I ran up to full throttle on the stick but it didn't sound like full throttle, I was pulling about 5 amps which was about half of what I expected. Then something on the board began to smoke and I moved the throttle stick all the down and the motor didn't shut off. I then unplugged the battery which was pretty tricky with a electic motor in my hand with a prop swinging. I took off the prop and took out the DVM, and tried it again. The motor just spins, at about a 50% rpm, servos still work (this is a all in one receiver / esc board). I guessing I fried the main transistor. Does this sound right? Nothing looks burnt on the board and nothing gets hot. The main transister is a NEC D882P. How do I tell if it is fired. Can I check something with a DVM? It looks ok from the outside, but the magic smoke came out of something.

Thanks,

Sympster

[Miami Mike]

Yes, you can check the transistor with your meter.

With no power applied to the circuit, put your meter in the diode check mode and check between the transistor leads, two at a time. If any pair of leads shows a near-zero reading and you get that same reading when you swap the meter leads, the transistor is shorted.

For a D882P (http://pdf1.alldatasheet.com/datasheet-pdf/view/127667/CDIL/CSD882P.html), pin 1 is the emitter, pin 2 is the collector, and pin 3 is the base. Normally, you'll get about a .5 reading in one direction and an open circuit indication in the other direction when reading between the base and collector, and you'll get about the same between the base and emitter.

I don't think that's your main power transistor though. It's only rated 3 amps!

[simingx]

Whatever released the smoke will probably have a "dimple" in it caused by the heat... a picture of the board might help.

[radio freak]

I have also had a similar problem with my receiver that came with a plane made in taiwn. The problem is not with the transistor D882P but with the power fet (mine had an IRFZ44N). just replace it and the controller should work normally.If the problem still persists ,please send me a detailed picture of your controller and then may be I can help you. :)

[Sympster]

OK, I checked the transistor, it's good. I agree, must be the power fet. However the servos aren't working now. I think the whole thing is going down hill fast. I have an electrical engineer at work, I ask him to look at it on Monday. Maybe he can figure something out. Thanks for your help.

-Sympter

[simingx]

The BEC might be smoked...

[Miami Mike]

The BEC might be smoked...Read it again. He said that his servos still work.

[simingx]

OK, I checked the transistor, it's good. I agree, must be the power fet. However the servos aren't working now. I think the whole thing is going down hill fast. I have an electrical engineer at work, I ask him to look at it on Monday. Maybe he can figure something out. Thanks for your help.

-Sympter

I don't think so.. :D

[Miami Mike]

Yes, he said that his servos still work, and now they don't. I doubt it's the BEC. It may be that the path on the PC board that the current takes from the battery is burned. Maybe it's a copper trace that was partially burned before and is completely open now.